For the microscopic examination of the tissue sections and other biological and botanical material, it is usually necessary to chemically treat sections of the material so that its structure can be observed under a microscope. This procedure is referred to as staining. Traditionally, a thin section of tissue or other biological material to be examined is mounted on a transparent slide which is retained on a horizontal surface, such as a laboratory workbench. The mounted section is then treated sequentially to a series of reagents which culminates in the specific staining of structural or composite features of the specimen. The choice of the reagents and the sequence in which they are applied to the specimen sections depends upon the nature of the specimen being examined and the particular features to be examined. Employing conventional staining techniques, a specimen is placed on a glass slide and a drop of the particular reagent being employed in the staining operation is placed on the specimen. Following a given contact period, the specimen is washed with distilled water or a buffered saline solution or the like to wash the reagent away and if required a drop of a second reagent placed on the specimen to continue or complete the staining procedure. Such manual methods do not always lend themselves readily to the processing of a large number of specimens by a single operator. For example, developments in the reagents employed has in many cases significantly reduced incubation times from a matter of days or hours to a matter of minutes. Consequently, it is very difficult for a single operator to stagger specimens reproducibly through the staining procedure and, consequently, an operator is only able to process a few specimens at a time.
Automation and batch staining techniques have been developed to improve the processing rate and increase the number of specimens which can be processed reproducibly by an operator. Automated techniques and devices, such as for example the "CODE-ON SLIDE STAINER" distributed by Fischer Scientific allow for automated processing and staining of many tissue sections. However, these devices are very costly and are normally available only to large institutional and commercial laboratories. Batch staining, on the other hand, markedly reduces the labor involved and also improves consistency and sensitivity. However, batch staining techniques presently involve the use of relatively large reagent volumes and incubation times of up to four days so that batch staining procedures are unpopular and normally impractical.